1. Technical Field
The present invention relates to a liquid ejecting head unit used in a liquid ejecting apparatus such as an ink jet recording apparatus and a liquid ejecting apparatus and, more specifically, to a liquid ejecting head unit which allows a liquid ejecting head to be mounted with high degree of positional accuracy with respect to a head fixing member and a liquid ejecting apparatus.
2. Related Art
A liquid ejecting apparatus includes a liquid ejecting head which is capable of ejecting liquid in the form of liquid droplets, and is an apparatus configured to eject various types of liquid from the liquid ejecting head. As a representative example of the liquid ejecting apparatus, for example, an image recording apparatus such as an ink jet recording apparatus (printer) provided with an ink jet recording head (hereinafter, referred to as “recording head”) and configured to perform recording by ejecting liquid state ink from nozzles of the recording head in the form of ink droplets may be exemplified. In recent years, not only the image recording apparatus, the liquid ejecting apparatus is also applicable to various manufacturing apparatuses such as a display manufacturing apparatus.
In recent years, as the printer as described above, there is a type employing a configuration (multiple head type) in which a plurality of recording heads each having a nozzle row made up of a plurality of nozzles arranged in a row and being arranged on and fixed to a head fixing member such as a sub carriage are unified as a single head unit. Then, in a configuration in which the respective recording heads are screwed to the sub carriage in a state of being positioned in place, provisional fixation securing of the recording heads to the sub carriage with adhesive agent (for example, instant adhesive) after positioning and before screwing is performed. Accordingly, displacement of the position of the recording heads at the time of real fixation by screwing due to angular moment generating when screwing is prevented. When employing the provisional fixation using the adhesive agent as described above, it is difficult to remove the recording head once fixed to the sub carriage for repair or replacement. In order to cope with such a problem, a configuration in which an intermediate member referred to as a spacer is interposed between the recording heads and the sub carriage is also proposed (for example, JP-A-2007-90327). In this configuration, the spacer is fixed to the recording head by screwing in advance, and the spacer and the sub carriage are provisionally fixed with the adhesive agent, and then the spacer and the sub carriage are really fixed by screwing, so that the recording head fixed once to the sub carriage can be removed from the spacer and the sub carriage by releasing tightening of the screw with respect to the spacer. Accordingly, mounting and demounting of the recording head for replacement, repair, or the like of the recording head is facilitated.
Incidentally, in the configuration in which the spacer is fixed to the recording head by screwing, deformation of the spacer or a spacer mounting portion of the recording head when the screw is tightened is prevented by bringing the both into abutment with each other without a gap at a point of screwing in a state before tightening the screw. Accordingly, since the shape of the spacer or the spacer mounting portion is stabilized, deformation of the spacer or the like when the screw is tightened is restrained even when screwing the spacer with respect to the sub carriage, so that the positional displacement of the recording head caused by the deformation is prevented. In contrast, when the contact surface between the recording head and the spacer is small due to downsizing of the recording head or the spacer, the recording head tends to incline with respect to the sub carriage specifically in the direction orthogonal to an imaginary line connecting the screw tightening points between the recording head and the spacer. For example, in the multiple head printer described above, the shape of the recording head is set to be short in the dimension in the direction of side-by-side arrangement of the heads on the sub carriage (the direction orthogonal to the nozzle row direction) and to be long in the dimension in the direction orthogonal to the direction of side-by-side arrangement of the heads (the direction orthogonal to the nozzle row direction) from the view point of minimizing the size of the head unit. Then, the respective recording heads are fixed to the spacer or the sub carriage on both sides in a long side direction (flange portions). With the recording head in this configuration, the direction orthogonal to the imaginary line connecting the tightening points with respect to each other corresponds to a short side direction, and hence the inclination tends to occur in this direction.
Cases which may cause the inclination described above include a case where an external force acts on the recording heads by contact of a landing target such as recording paper, a case where variations in dimension of parts occur, and a case where thermal expansion occurs when the temperature rises. When such an inclination occurs, even when the recording heads are arranged at prescribed positions with respect to the sub carriage on a flat plane, the flying directions of ink ejected from the nozzles are deviated from desired original directions, so that the positional accuracy of ink landing on the landing target such as the recording paper is disadvantageously lowered.
Such a problem exists not only in the ink jet recording apparatus having the recording heads for ejecting ink mounted thereon, but also in other liquid ejecting head units employing a configuration in which the liquid ejecting head is fixed to the head fixing member such as the sub carriage via the intermediate member such as the spacer, and the liquid ejecting apparatus having the same.